Owners of the 100-story John Hancock Center said the building's namesake, the insurance company that built the tower almost five decades ago, asked that its name and logos throughout the building's interior be removed immediately.

The Hancock is the city's fourth-tallest building, at 1,128 feet.

For now the building will be known by its address, 875 N. Michigan Ave., as the owner seeks a new naming-rights deal, said Stephen Hearn, president and CEO of Hearn Co.

Chicago-based Hearn is part of a group of real estate investors that has owned the office and parking portions of the building since 2013.

John Hancock removed its name from the 62-story John Hancock Tower in Boston in 2015 after its last office lease in the building expired.

The insurer, which was acquired by Toronto-based Manulife Financial in 2004, hasn't been a tenant in Chicago's John Hancock Center for many years.

"As they did in Boston, they just decided to have their name removed," Hearn said. "At this point, we'll push harder for a replacement name. This property deserves a more important identity than simply the address."

John Hancock hasn't paid for the right to have its name on the modernist skyscraper since the last naming-rights contract expired shortly after the current owners bought it, Hearn said.

Manulife representatives did not immediately respond to requests for comment.

John Hancock Mutual Life Insurance Co. built the tower from 1965 to 1970. The building, designed by Skidmore, Owings & Merrill, is known for its black, X-shaped braces.

The loss of the iconic name comes as Hearn decided to continue owning the property after exploring a potential sale. Hearn has decided to hold on to the property for at least another two or three years, meaning it will likely be the owner that signs a naming-rights deal.

Hearn and its investment partners, Mount Kellett Capital Management and San Antonio-based Lynd Co., bought their portion of the tower for $140 million in 2013. Mount Kellett is now an affiliate of New York-based Fortress Investment Group.

The group owns the 717-space parking garage on Floors 4 to 12 and about 908,000 square feet of offices on Floors 13 to 41.

The group invested about $69 million on building upgrades and signing new leases.

Other portions of the property - including residential condominiums, retail and restaurant space, broadcast antennas and the 360 Chicago observatory - are owned separately.

The Tribune reported last year that the office and parking owners were putting the property up for sale, with offers expected to potentially top $330 million.

But offers came in lower than hoped amid a continued slowdown in downtown Chicago office sales in 2017. Last year's downtown office sales volume was $2.2 billion, according to Jones Lang LaSalle, down from $2.5 billion in 2016. The past two years were down dramatically from a record $6.5 billion in sales in 2015.

Hearn said several factors, including uncertainty over future interest rates and the impact of new tax laws, slowed the potential sale of its building as well as other large office deals in Chicago.

"It all led to the notion that this isn't the right time for a sale," Hearn said.

The owners instead will look to refinance the property with a new loan, he said.

Hearn will continue talks for naming rights, which he said could be tied into a redevelopment of the ground-floor plaza. The plaza, parking garage and naming rights are controlled by the office owner.

Hearn previously estimated naming rights could be worth $1.5 million or more annually.

Yet he said he realizes name changes should not be taken lightly, conscious that many Chicagoans refuse to refer to the former Sears Tower by its nearly decade-old moniker, Willis Tower.

Hearn declined to say whether he expected the building's new namesake to be a tenant in the building.

Circumstances at the Hancock differ from those that led to the Sears Tower becoming Willis Tower in 2009. In that deal, British insurance broker Willis Group Holdings acquired naming rights as part of an office lease.

In the Hancock's case, the building's namesake has asked for a change without a replacement in tow.

"We have turned away a number of interested parties because we didn't feel the name was appropriate for this iconic property," Hearn said. "I want to put an identity on this property that everyone in Chicago can be proud of."